Miniature projection devices, which are also commonly referred to as portable projection devices or pocket type projection devices, are used for displaying images and colors. The core structure of a miniature projection device is an optical display system including a display module and a lens module. Optical display systems are very sensitive to dust and pollution of optical display systems will affect the image display quality. A miniature projection device will fail to function normally if such pollution reaches a certain degree, making dustproof designs for miniature projection devices crucially important. However, development of miniature projection devices is still in its infancy, with current dustproof designs focusing on sealing of the housings and packaging of the optical display systems in the housings. Such dustproof designs are not conducive for heat dissipation and diopter and interpupillary distance adjustment typically require openings to be provided to the housing, interfering with this sealing. Therefore, to adapt to the development of miniature projection devices, dustproof structures that provide a higher level of protection from dust without restricting the provision of openings to the housings are urgently needed.